社会的ディレンマとTIT FOR TAT : Axelrodの諸定理の批判的検討
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概要
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The games of prisoner's dilemma (PD) and iterated prisoner's dilemma (IPD) have attracted the attention of many social scientists because these games are believed to represent the basic structure of such global social dilemmas as the nuclear arms race, environmental pollution, and the population explosion. Recently, biologists came to notice in these games the issue of selfishness vs. altruism which is one of the fundamental problems of social evolution. So the question of how cooperation develops in a world of egoists is now the object of common concern for both social scientists and biologists. Axelrod, a political scientist, in collaboration with Hamilton, a biologist, have made important contributions in these areas. He demonstrated by means of a couple of computer tournaments the superiority of TIT FOR TAT (TFT), which was one strategy among various strategies in a game of IPD. TFT is a strategy which never defects first but retaliates immediately when defected. It guarantees a cooperating society if it predominates, but the question is how and when it assumes dominance. Axelrod tried to answer these questions by proving eight theorems dealing with TFT and other strategies in IPD. The purpose of the present paper is to critically examine Axelrod's theorems and to discuss a few fundamental problems of social evolution. The paper begins with the definition of several concepts of game theory and Maynard Smith's evolutionary game theory which are prerequisites to Axelrod's theory, and then examines Axelrod's theorems, one by one. The main conclusions are: (i) Although Axelrod's theorems establish the conditions for the emergence of TFT among egoists and for the stability of TFT dominance, they lack the theory of dynamic process which connects the emergence and the dominance of TFT; (ii) to fill the gap, the definition of cluster given by Axelrod can be modified and the cluster theorem can be reformulated; (iii) the stability condition of TFT dominance is intrinsically related to Hamilton's rule of kin selection, and this relationship may properly be extended to the broader concept of assortative interaction.
- 東京女子大学の論文
- 1986-09-15